A number of processes for the production of bituminous binders of the aforementioned type are known by which an improvement in properties is accomplished when ordinary bitumen is combined with addition of a thermoplast or thermoplastic material. Such modifying of the bitumen often requires a re great labor expenditure because a number of different thermoplasts, whose addition to bitumen is capable of improving its properties considerably, are not readily soluble in bitumen. Although there does exist thermoplast materials suitable for the modification of bitumens which have better solution properties in bitumens, these thermoplasts often have a relatively high acquisition price. Moreover, construction materials produced with such soluble thermoplasts often have lower physical strength than those construction materials whose binder is a bitumen treated with the relatively non-soluble thermoplasts.